A gas turbine engine, such as a gas turbine engine for an aircraft, includes a compression section, a combustion section and a turbine section. A flowpath for hot gases extends axially through the engine. The flowpath for hot gases is annular in shape. An engine case extends axially through the sections of the engine and circumferentially about the flowpath to bound the working medium flowpath.
As the working medium gases are flowed along the flowpath, the gases are compressed in the compression section causing the temperature and the pressure of the gases to rise. The hot, pressurized gases are burned with fuel in the combustion section to add energy to the gases. These gases are expanded through the turbine section to produce useful work and thrust.
The combustion section includes a combustion chamber and one or more fuel nozzles disposed in the combustion chamber for supplying fuel to the combustion chamber. The combustion chamber may be annular in shape and has an upstream end which is adapted by openings to receive a major portion of the hot, working medium gases discharged from the compression section. The gases are mixed with fuel (typically a combustible fluid such as JP4). The gases and fuel are ignited to produce gases whose temperature can exceed twenty-five hundred (2500) degrees Fahrenheit.
Each fuel nozzle assembly has a fuel nozzle or fuel nozzle head for discharging fuel into the combustion chamber. The fuel nozzle head includes a heat shield which extends circumferentially about the fuel nozzle head to shield the end of the fuel nozzle head from the hot, working medium gases in the combustion chamber.
One example of a fuel nozzle head 50 of the prior art having a heat shield 52 is shown in FIG. 3 and FIG. 3a. The fuel nozzle head includes a fuel nozzle tip 54 extending about an axis A. A plurality of swirl vanes 56 extend outwardly from the fuel nozzle tip. A swirler housing assembly is integrally joined to the swirl vanes. The swirler housing assembly engages the heat shield.
The swirler housing assembly 58 has a shoulder 60 which extends circumferentially about the assembly and which adapts the assembly to receive the heat shield. The shoulder has a first surface 62 which extends radially and a second surface 64 which extends axially. The heat shield has a base 66 which is adapted by corresponding surfaces 67, 68 to engage the swirler housing assembly.
As shown in FIG. 3a, the method of assembly includes focusing a beam of electrical current (electron beam weld) on the base of the heat shield and the swirler housing assembly at the adjacent surfaces 62, 64 to bond these surfaces together. The beam must penetrate and extend past the juncture of the surfaces in the heat shield to ensure that the weld is circumferentially continuous at its innermost dimension about the circumference of the assembly to avoid cracking. As a result, the base is attached to the first surface and the second surface of the swirler housing assembly.
This construction and method of assembly notwithstanding, scientists and engineers working under the direction of Applicant's assignee are seeking to improve fuel nozzle assemblies, and particularly, the heat shield and the method of installing the heat shield to the fuel nozzle assembly.